The European Commission (EC) has proposed expanding the European Defence Fund, an initiative to fund defense technology developed in Europe. As a general matter, only European firms would have access to the fund for development, and participating European nations would need to commit themselves to purchasing the defense materiel developed under the fund. In effect, this could lock U.S. firms out of billions of euros worth of European defense procurement over the coming years—despite long-standing reciprocal agreements under which the U.S. and its European allies agreed to open their defense markets. The fund was announced quietly last year and now, in the shadow of a trade war launched by the Trump administration, has evolved into a substantial potential barrier in the transatlantic defense market, and potentially another brick in a rising wall of protectionism between the U.S. and Europe.